Variable switch



D. E. HEERDT VARIABLE SWITCH July 31, 1962 2 Sheets-Sheet l FiledJuly 1o, 1959 July 31, 1962 Filed July l0, 1959 D. E. HEERDT 3,047,684

VARIABLE SWITCH 2 Sheets-Sheet 2 United States Patent 3,047,684 VARIABLE SWITCH Donald E. Heerdt', Cicero, Ill., assignor to Ferro Corporation, a corporationV of' Ohio Filed July 10, 1959, Ser. No. 826,255 Claims. (Cl. 200-38) This invention relates to a variable switch and` more particularly to an inlnitely variable switch with a control mechanism for varying the portion of time the switch contacts are closed.

A- problem with electric ranges is in controlling the application of power to the heating element to provide a wide range of cooking temperatures. Multi-element heating units afford different series andy parallel combination of the resistance elements providing a limited degree of control. Thermostat-ic control devices are available which hold the temperature of the unit or the pan being heated within very close limits; they are, however, relatively expensive. It has previously been proposed that an adjustable cam switch be rconnected in the heating element circuit opening and closing the circuit periodically, controlling the average power supplied to the element. For example, a cam is driven at a predetermined rate, as one revolution per minute, and switch contacts associated therewith open `and close at periodic intervals with the closed time being determined by the position of the switch relative to the cam. rIhis mechanism is rather difficult to calibrate in a manner providingthe user with an accurate indication ofthe temperature of the unit, and is quite sensitive to wear and aging of the parts so that the initial calibration rapidly becomes inaccurate.

It is a principal object of this invention to provide an improved variable switch which is positive in action and has no critical surfaces which may wear and cause the switch to lose calibration.

One feature of the invention is a switch which includes a pair of contacts one movable with respect to .the other between open and closed positions, periodically operable means for moving the movable contact from one position to the other, means for latching the movable contact in ythe other position and means for releasing the latching means. More particularly, the mechanism includes a rotating cam which positively closes the switch contacts periodically, together with an adjustable release mechanism which releases the latching means, opening the switch a predeternuned'period after it is closed'by the cam.

Another feature is that the latching means are spring urged into latching positionand release means are periodically operative for deflecting the spring toY release the switch. A further feature is 'that the latch comprises a slider mounted on a pin and movable generally transversely to Ithe `direction'of`movement of. the movable switch member, and spring means are. provided for moving the slider into and out of latching. position.

Still another feature is that a latch operating arm is engaged with the latch member and carried by a pivotally mounted ring with a moving springurging the ring in a direction to hold the operating arm laway from engagement with the latching member, andthe switch includes control means for deecting the moving spring to release the ring and operating arm which retracts` the latch. Yet a further feature is that the spring deflecting ice control means are adjustable in position toA control the length of time the switch contacts: are latched in the closed position.

Further features and advantages willI readily be ap parent from the following specication andr fromv the drawings, in which:

FIGURE 1 is a plan View of a .switch embodying. the invention and mounted in a casing with thecover removed;

FIGURE 2 is an exploded perspective view of the cam, control disc and latch operating member;

FIGURE 3 is an enlarged fragmentary section taken generally along line 3 3 of FIGURE 1;

FIGURE 4 is an enlarged fragmentary section taken generally along line 4 4 of FIGURE l;

FIGURE 5 is an enlarged fragmentary section taken generally along line 5 5 of FIGURE 1;

FIGURE 6 is an enlarged elevation of the cam, operating member ring andy control disc; and

FIGURE 7 is an enlarged fragmentary plan of the switch and latch. l

The embodiment of a variable switch disclosed herein is intended for use in controlling the surface element of an electric range and will be described in connection with such a unit. lst will be understood that the switch may be used in other circuits where it is desired to vary the duty cycle of `the load.

Turning now to FIGURE l of the drawings, a circuit is shown including a heating element 20` Iand a motor 21, connected with one terminal 22 of a powersource. The other source terminal 23 is connected through the switch mechanism, indicated generally at 24, completing., cir cuits to heating element 20 and motor 21 as will bey described. Switch mechanism 24 is housed within a casing 25 and includes a line switch 26 comprising fixed and movable contacts 26aV and 26b', respectively, and a timing switch 2,7 having fixed and movable contacts 27a and 27b, respectively. The circuit of heating element 2.0i is completed through both switches 27' and 26, connectedI in series while the circuit of motor 21 iscompleted directly through line switch 26. ln FGURE 1 the switch is shown in its off position with the contacts of both switches open.

Movable contact 2Gb of line switch 26 is`mounted on a leaf 28 having a bearing portion 28a formed therein which rests on the peripherall surf-ace` of a disc-shaped control member 29 and in the olf position enters a depression 29a`formed therein separating-contacts 26a and 26'b. When control disc 29 is rotated awayfrom its off positionswitch 26 closes completing the circuit of motor 21 which in turn drives a cam32;

Control switch 27 includes a leaf blade 3'3 on which the movable contact 27h is carried. A followeror switch actuator 34 is connected with switch leafv near its mounting 33a and extends generally parallel With the' switch leaf. Movement of follower 34 is transmitted to switch leaf 33, closing and opening the switch.

As cam 32 turns (here in a-clockwise-direction) a raised cam surface 32a comes into cont-act with the bearing surface 34a of switch follower 34 and moves boththe follower and switch leaf 33 in a counterclockwise direction closing contacts 27a and 27b. A latch'mechanism, indicatedy generally at 35 is associated With the freeouter end 3.4111 of switch follower 34 holding iti in a position maintaining the contacts closed.

Asbest seen in FIGURES 3 and 7, the latch mechanism includes a spool shaped slider 37 carried on a pin 38 extending outwardly from the bottom surface of casing 25 and urged away from the casing by leaf spring 39 which has a bifurcated end portion 39a straddling pin 38. When cam 32 forces switch follower 34 to the right closing contacts 27a and 27b the end 34b of the switch fol-lower moves beyond the edge surface of latch 37 which is forced outwardly by spring 39 behind the follower and holds the follower `and movable contact 27b in closed position.

A latch slider operating mechanism includes an operating arm 42 having a bifurcated end portion 42a embracing slider 37 above lower flange 37a. Operating arm 42 is carried on a ring 43 pivotally mounted in the casing on a pair of spaced extensions or mounting arms 44. As best seen in FIGURES 2 and 6 an arcuate leaf spring 45 is secured to the upper surface of cam 32 underlying ring 43 and urging it upwardly holding arm end 42a above slider flange 37a. A projection 46 on the under surface of control member 29 is positioned to engage leaf spring 45 at some point in its rotation, forcing it down toward the surface of cam 32. This removes the support for ring 43 'and leaf spring 43, the free end of which overlies the surface of operating member 42 forces the operating arm down against the action of leaf spring 39 retracting the `latching slider 37, releasing follower 34 and opening switch 27. (FIGURE l and the broken line showing of FIGURE 7.)

The operation of the switch repeats upon each revolution of the cam 32. First, raised cam surface 32a acts through follower 34 closing switch 27 and complet- -ing the circuit to heating element and as the switch closes the free end 34b of the switch follower is latched in the closed position by slider 37. With further rotation of cam 32, leaf spring 45 is forced downwardly by projection 46 on the undersurface of control member 29 releasing ring 43 and permitting spring 48 to overcome the effect of spring 39 moving latch slider 37 downwardly and releasing switch follower 34b.

Control member 29 is provided with a shaft 52 extending outwardly through the cover a of casing 25, by means of which the position of projection 46 relative to the point at which switch 27 is closed, may be varied, controlling the point in the cycle at which the switch is released, controlling the duty cycle of the system and the temperature to which element 2t) is heated. The peripheral surface 2912 of the control disc is illustrated as serrated. These serrations engage the bearing surface 28a of line switch 26 and aid in positioning the control member.

It will be noted that the end 34b of switch follower 34 overlies slider 37 when lthe switch is in the open posi- Ition. This prevents the slider from moving outwardly far enough to block movement of the follower from the open to the closed switch position.

As best seen in FIGURES 4 and 5, the outer ends of mounting projections 44 are formed with loops `44a which receive a transverse pin 55. The pins are received in a pair of recesses 56 provided along. the wall of casing 25 and held in place by retainer 57.

Switch 27 is actuated positively to complete the circuit and the movable switch contact is latched in closed position. At the end of the desired on portion of the cycle the latch is positively released and the spring action 0f the leaf switch member quickly and positively opens the circuit. The only critical surface in the mechanism is that of the projection 46 on the lower side of the control disc 29. This surface receives very little wear from its contact with spring 45 and once the switch is calibrated it retains its calibration.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes therefore in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. A switch comprising: a fixed contact; a contact associated with said fixed contact, movable between open and closed positions and spring urged toward said open position; a timer cam Afor moving said movable contact to said closed position periodically; means for latching said movable contact in said closed position; and control means for releasing said latching means.

2. The switch of claim l, wherein said control means is adjustable.

3. A switch comprising: a fixed contact; a spring urged movable contact associated with said fixed contact and movable between open and closed positions; means for periodically latching said movable contact in the closed position for a predetermined time; and means including a control disc, synchronized with said latching means for periodically releasing said latching means and controlling the time that said switch contacts are latched in a closed position.

4. A switch comprising: a fixed contact; a movable contact associated with said iixed contact and movable between open and closed positions; periodically operable control means for moving said movable contact from one position to another; a spring, urging a latching means to hold said movable switch member in said other position; and periodically operative means for deliecting said spring to release said movable switch member.

5. The switch of claim 4, wherein said latch member comprises a slider on a pin, movable generally transversely to the direction of movement of said movable switch member, said switch member having a surface engageable with said slider.

6. A switch comprising: a fixed contact; a movable contact associated with said fixed contact and movable between open and closed positions; periodically operable control means for moving said movable contact from `one position to the other; a latching member for holding said movable switch member in said other position; a latch operating arm mounted on a supporting ring and engaged with said latch member; a leaf spring urging said operating arm in a direction away from engagement with said latching member; and means having `a surface for deliecting said leaf spring releasing said operating `arm to retract said latch member.

7. A switch comprising: a fixed contact; a movable contact associated with said fixed contact and movable between open and closed positions; periodically operable control means for moving said movable contact from one position to 'the other; a latching member for holding said movable switch member in said other position; a latch operating arm engaged with said latch member; a ring having said arm mounted thereon; a moving spring urging said ring in a direction to hold said operating arm away from engagement with said latching member; `and means having a surface for detlecting said spring releasing said ring and operating arm to retract said latch member.

8. The switch of claim 7, wherein said ring is provided with a pair of mounting arms extending therefrom generally opposite said operating arm and pivotally mounted at the ends thereof.

9. A switch comprising: a fixed contact; a movable Contact associated with said fixed contact and movable between open and closed positions; periodically operable control means for moving said movable contact from one position to ythe other; a latching member including a slider on a pin moving generally transversely to the direction of the movable switch member for holding said movable switch member in said other position; a latch operating Iarm mounted on a supporting ring and engaged with said latch member; -a spring associated with said control means urging said operating arm in a direction away from engagement with said latching member; means having a surface for deecting said spring releasing said operating arm to retract said latch member; and another spring urging said member in the opposite direction.

10. A switch comprising: a fixed contact; a leaf mounted contact associated with said -xed contact, movable between open and closed positions; a follower vmember for said switch; a timer cam engaging said follower member for moving said leaf contact from one of said positions to the other of said positions periodically; means References Cited in the file of this patent for latching said Imovable contact -in said other position; 10 2,943,159

and control means `for releasing said latching means.

UNITED STATES PATENTS Lux July 19, 1932 Grayson Jan. 24, 1939 Harris Nov. 8, 1955 Laviana Jan. 22, 1957 Goodhouse Apr. 29, 19518 Goodhouse June 28, 1960 

